1. Field of the Invention
The invention relates to methods for forming a metal oxide film on a polymeric substrate.
2. Description of the Related Art
Transition metal oxides have gained considerable interest recently due to their potential application in solar cells (see, Maruyama, Solar Energy Mater. Solar Cells 56 (1998) 85), heterogeneous catalysis (see, Li et al., J. Phys. Chem. C, 112 (2008) 19040), gas sensors (see, Ishihara et al., J. Mater. Chem., 8 (1998) 2037), and supercapacitors (see, Huang et al., Electrochimica Acta 75 (2012) 208). Among transition metal oxides, copper oxides are non toxic and the abundant availability of copper makes copper oxides a cheap material for many applications. Cupric oxide is a p-type semiconductor with an indirect band gap of 1.2-1.5 eV (see, Marabelli et al., Phys. Rev. B: Condens. Matter, 52 (1995) 1433). The application of CuO as a selective absorbing layer in solar cells has been reported because of its high solar absorption.
Polymeric substrates offer added advantages over traditional rigid substrates like glass in terms of light weight and flexibility. However, fabrication of devices on flexible substrates is a challenge owing to the low temperature tolerance of the polymers. Typically, high temperatures are required to grow semiconducting oxides like copper oxide. This limits the growth of these oxides on polymer substrates like polyethylene napthalate.
Therefore, what is needed is an improved method for forming a metal oxide film on a polymeric substrate.